DCI Hannah Scarlett heads Cumbria Constabularyís Cold Case Review Team, and first appears in The Coffin Trail. The team is newly formed, but Hannah fears she is being shunted into a backwater by her ambitious boss, ACC Lauren Self, following her involvement in a trial that collapsed, allowing the accused to walk free. However, her loyal ally DS Nick Lowther joins her in the cold case unit, and another recruit on a short-term contract is Les Bryant, a retired cop from Yorkshire, whose grumpy manner conceals vast experience.
In the early years of her career in the police, Hannah was mentored by Ben Kind, and over the years, they developed a close yet platonic relationship. Benís death causes Hannah much grief, but she is fascinated when Benís son, the historian Daniel Kind, moves to the Lake District. They meet in Kendal, and become intrigued by each other.
Their friendship is complicated by the fact that, at the start of the series, both of them are in other relationships. Daniel is with Miranda, with whom he buys a cottage in Brackdale, and Hannah is living with second hand book dealer Marc Amos.
After the events described in The Coffin Trail, Hannahís path keeps crossing with Danielís Ė in The Cipher Garden, when an anonymous letter prompts her to investigate the murder of landscape gardener Warren Howe, and in The Arsenic Labyrinth, when she looks into the mysterious disappearance ten years ago of a young woman who lived in Coniston. As the pair get to know each other better, they find themselves drawn into an increasingly dangerous liaison.